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std::condition_variable::wait_for

提供: cppreference.com

 
 
スレッドのサポートライブラリ
スレッド
Original:
Threads
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thread(C++11)
this_thread空間
Original:
this_thread namespace
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get_id(C++11)
yield(C++11)
sleep_for(C++11)
sleep_until(C++11)
相互排除
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Mutual exclusion
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mutex(C++11)
timed_mutex(C++11)
汎用のロック管理
Original:
Generic lock management
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lock_guard(C++11)
unique_lock(C++11)
defer_lock_t
try_to_lock_t
adopt_lock_t
(C++11)
(C++11)
(C++11)
lock(C++11)
try_lock(C++11)
defer_lock
try_to_lock
adopt_lock
(C++11)
(C++11)
(C++11)
条件変数
Original:
Condition variables
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condition_variable(C++11)
condition_variable_any(C++11)
notify_all_at_thread_exit(C++11)
cv_status(C++11)
先物
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Futures
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promise(C++11)
future(C++11)
shared_future(C++11)
packaged_task(C++11)
async(C++11)
launch(C++11)
future_status(C++11)
future_error(C++11)
future_category(C++11)
future_errc(C++11)
 
std::condition_variable
メンバ関数
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Member functions
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condition_variable::condition_variable
condition_variable::~condition_variable
通知
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Notification
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condition_variable::notify_one
condition_variable::notify_all
待っています
Original:
Waiting
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condition_variable::wait
condition_variable::wait_for
condition_variable::wait_until
ネイティブハンドル
Original:
Native handle
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condition_variable::native handle
 
template< class Rep, class Period >

std::cv_status wait_for( std::unique_lock<std::mutex>& lock,

                         const std::chrono::duration<Rep, Period>& rel_time);
(1) (C + + 11以来)
template< class Rep, class Period, class Predicate >

bool wait_for( std::unique_lock<std::mutex>& lock,
               const std::chrono::duration<Rep, Period>& rel_time,

               Predicate pred);
(2) (C + + 11以来)
1)
アトミックlock、ブロックは現在実行中のスレッドを解放し、*thisで待機しているスレッドのリストに追加します。スレッドがnotify_all()またはnotify_one()実行されたときにブロックが解除、または相対タイムアウトrel_timeは、期限切れになったときにされます。また、偽ってブロックを解除することができる。ブロックを解除する場合は、理由に関わらず、lockは再取得さwait_for()終了です。例外によってこの関数が終了した場合は、lockも再取得される.
Original:
Atomically releases lock, blocks the current executing thread, and adds it to the list of threads waiting on *this. The thread will be unblocked when notify_all() or notify_one() is executed, or when the relative timeout rel_time expires. It may also be unblocked spuriously. When unblocked, regardless of the reason, lock is reacquired and wait_for() exits. If this function exits via exception, lock is also reacquired.
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2)
に相当する
Original:
Equivalent to
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while (!pred())
    if (wait_for(lock, rel_time) == std::cv_status::timeout)
        return pred();
return true;

このオーバーロードは、スプリアスの覚醒を無視するために使用されるかもしれません.
Original:
This overload may be used to ignore spurious awakenings.
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目次

[編集] パラメータ

lock -
現在のスレッドによってロックされなければなりません型std::unique_lock<std::mutex>のオブジェクト
Original:
an object of type std::unique_lock<std::mutex>, which must be locked by the current thread
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rel_time -
型のオブジェクトstd::chrono::duration待って過ごす時間の最大値を表す
Original:
an object of type std::chrono::duration representing the maximum time to spend waiting
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pred - predicate which returns ​false
待機している場合は、継続すべきである
Original:
if the waiting should be continued
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.

The signature of the predicate function should be equivalent to the following:

 bool pred();

[編集] 値を返します

1)
std::cv_status::timeoutによって指定された相対的なタイムアウトの期限が切れるrel_time場合、std::cv_status::no_timeout並外れて賢明な.
Original:
std::cv_status::timeout if the relative timeout specified by rel_time expired, std::cv_status::no_timeout overwise.
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2)
falsepredタイムアウトが期限切れになった後に述語falseはまだrel_timeに評価された場合は、そうでなければtrue.
Original:
false if the predicate pred still evaluates to false after the rel_time timeout expired, otherwise true.
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[編集] 例外

std::system_errorをスローする可能性があり、またlock.lock()またはlock.unlock()によってスローされた例外を伝播する可能性.
Original:
May throw std::system_error, may also propagate exceptions thrown by lock.lock() or lock.unlock().
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[編集] ノート

lock.mutex()が現在のスレッドによってロックされていない場合は、この関数を呼び出すと、未定義の動作です.
Original:
Calling this function if lock.mutex() is not locked by the current thread is undefined behavior.
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lock.mutex()は現在同じ条件変数で待っている他のすべてのスレッドが使用するものと同じミューテックスない場合は、この関数を呼び出すと、未定義の動作です.
Original:
Calling this function if lock.mutex() is not the same mutex as the one used by all other threads that are currently waiting on the same condition variable is undefined behavior.
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[編集]

#include <iostream>
#include <atomic>
#include <condition_variable>
#include <thread>
#include <chrono>
 
std::condition_variable cv;
std::mutex cv_m;
std::atomic<int> i = ATOMIC_VAR_INIT(0);
 
void waits(int idx)
{
    std::unique_lock<std::mutex> lk(cv_m);
    if(cv.wait_for(lk, std::chrono::milliseconds(idx*100), [](){return i == 1;})) 
        std::cerr << "Thread " << idx << " finished waiting. i == " << i << '\n';
    else
        std::cerr << "Thread " << idx << " timed out. i == " << i << '\n';
}
 
void signals()
{
    std::this_thread::sleep_for(std::chrono::milliseconds(120));
    std::cerr << "Notifying...\n";
    cv.notify_all();
    std::this_thread::sleep_for(std::chrono::milliseconds(100));
    i = 1;
    std::cerr << "Notifying again...\n";
    cv.notify_all();
}
 
int main()
{
    std::thread t1(waits, 1), t2(waits, 2), t3(waits, 3), t4(signals);
    t1.join(); t2.join(), t3.join(), t4.join();
}

Output:

Thread 1 timed out. i == 0
Notifying...
Thread 2 timed out. i == 0
Notifying again...
Thread 3 finished waiting. i == 1

[編集] も参照してください

条件変数はウェイクアップされるまで、現在のスレッドをブロックします
Original:
blocks the current thread until the condition variable is woken up
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(パブリックメンバ関数) [edit]
条件変数はウェイクアップされるまで、または指定された時点に達するまで、現在のスレッドをブロックします
Original:
blocks the current thread until the condition variable is woken up or until specified time point has been reached
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(パブリックメンバ関数) [edit]